Baltisk Crater is a crater in the Argyre quadrangle of Mars. It is located at 42.7° South and 54.7° West, is 52 km in diameter, and was named after a town in Russia.[1]

Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than 10 km in diameter) they usually have a central peak.[2] The peak is caused by a rebound of the crater floor following the impact.[3]

Dunes in Baltisk Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of a previous image.

Fans in Baltisk Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of a previous image. Arrows point to layered parts of the fans.

Many craters once contained lakes.[4][5][6] Because some crater floors show deltas, we know that water had to be present for some time. Dozens of deltas have been spotted on Mars.[7] Deltas form when sediment is washed in from a stream entering a quiet body of water. It takes a bit of time to form a delta, so the presence of a delta is exciting; it means water was there for a time, maybe for many years. Primitive organisms may have developed in such lakes; hence, some craters may be prime targets for the search for evidence of life on the Red Planet.[8]